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Document Server@UHasselt (41,057 recursos)
Repository of the University of Hasselt containing publications in the fields of statistics, computer science, information strategies and material from the Institute for behavioural sciences.

Dept. Chemistry-Biology-Geology (SBG) - Laboratory of Inorganic and Physical Chemistry

Mostrando recursos 1 - 20 de 272

1. Solution derived ZnO:Al films with low resistivity - SCHELLENS, Kevin; Capon, B.; DE DOBBELAERE, Christopher; Detavernier, C.; HARDY, An; VAN BAEL, Marlies
ZnO:Al thin films were prepared via chemical solution deposition, using 2-butoxyethanol as an alternative for 2-methoxyethanol, which is more commonly used, but acutely toxic. The precursor solutions can be readily spin coated. The phase, morphology, electrical and optical properties of the deposited films are investigated, by XRD (X-ray diffraction), scanning electron microscopy, a two-point contact measurement and UV-vis spectrophotometry respectively. This way, the effect of this solvent is investigated. The films are deposited on borosilicate glass substrates and were found to be continuous and smooth. XRD measurements show a highly preferential c-axis orientation. The effects of the thermal treatment profile...

2. Towards high-performance biopackaging: barrier and mechanical properties of dual-action polycaprolactone/zinc oxide nanocomposites - ELEN, Ken; Murariu, M.; Peeters, R.; Dubois, Ph; MULLENS, Jules; HARDY, An; VAN BAEL, Marlies
The properties of nanocomposites of biodegradable polycaprolactone containing zinc oxide (ZnO) nanoparticles with diverse morphologies, that is, ZnO nanospheres, nanorods, and nanodisks are investigated. It is demonstrated for the first time that the dual action of the ZnO nanoparticles reduces the gas permeability of the nanocomposites via two mechanisms: first by the creation of a tortuous path and second by gas adsorption. Depending on the morphology of the particles, the oxygen permeability can be reduced by more than 60%. Tensile tests show that the nanocomposites remain very ductile. The nominal strain for all nanocomposites is higher than 500% before fracture...

3. Luminescence of LaF3:Ln3+ Nanocrystal Dispersions in Ionic Liquids - Lunstroot, Kyra; Baeten, Linny; Nockemann, Peter; Martens, Johan; Verlooy, Pieter; Ye, Xingpu; Görller-Walrand, Christiane; Binnemans, Koen; Driesen, Kris
Ionic liquids were used as solvents for dispersing luminescent lanthanide-doped LaF3:Ln3+ nanocrystals (Ln3+ ) Eu3+ and Nd3+). To increase the solubility of the inorganic nanoparticles in the ionic liquids, the nanocrystals were prepared with different stabilizing ligands, i.e., citrate, N,N,N-trimethylglycine (betaine), and lauryldi- methylglycine (lauryl betaine). LaF3:5%Ln3+:betaine could successfully be dispersed in 1-butyl-1-methylpyr- rolidinium bis(trifluoromethylsulfonyl)imide [C4mpyr][Tf2N], 1-butyl-1-methylpyrrolidinium trifluoromethane- sulfonate [C4mpyr][TfO], and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [C4mim][Tf2N] but only in limited amounts. Red photoluminescence was observed for the europium(III)-containing nanoparticles and near-infrared luminescence for the neodymium(III)-containing systems.

4. Tuning the Dimensions of ZnO Nanorod Arrays for Application in Hybrid Photovoltaics - Baeten, Linny; Conings, Bert; D'Haen, Jan; De Dobbelaere, Christopher; Hardy, An; Manca, Jean V.; Van Bael, Marlies K.
ZnO nanorod arrays are a very eligible option as electron acceptor material in hybrid solar cells, owing to their favorable electrical properties and abundance of available, easy, and low-cost synthesis methods. To become truly effective in this field, a major prerequisite is the ability to tune the nanorod dimensions towards optimal compatibility with electron-donating absorber materials. In this work, a water-based seeding and growth procedure is used to synthesize ZnO nanorods. The nanorod diameter is tuned either by modifying the zinc concentration of the seeding solution or by changing the concentration of the hydrothermal growth solution. The consequences of this...

5. Relation between Morphology and Recombination Kinetics in Nanostructured Hybrid Solar Cells - Conings, Bert; Baeten, Linny; Boyen, Hans-Gerd; D'Haen, Jan; Van Bael, Marlies K.; Manca, Jean
Systematic performance improvement of excitonic solar cells hinges on thorough knowledge of their main loss mechanisms. Accordingly, the study of recombination kinetics is indispensable, enabling to identify and quantify what is considered the most important loss pathway for such devices. In contrast to the advances made in controlling the morphology of organic bulk heterojunction solar cells, it remains challengin to establish a robust correlation between morphology and recombination kinetics. Most obvious culpritsare the rather disordered nature of most heterojunctions and the absence of phase purity. In that respect, hybrid solar cells based on ZnO nanorod arrays and poly(3- hexylthiophene) can o???er a convenient...

6. Dewetting of Patterned Silicon Substrates Leading to a Selective Deposition of Micellar-Based Nanoparticles - Riskin, Alexander; De Dobbelaere, Christopher; Shan, Lianchen; Boyen, Hans-Gerhard; D'Haen, Jan; Hardy, An; Van Bael, Marlies K.
We have applied soft lithography for the indirect patterning of micellar poly(styrene-b-2-vinyl pyridine) diblock copolymers loaded with gold chloric acid with a pattern width below a micrometer. A combination of physical and chemical heterogeneities on the substrate induced a selective deposition of the micelles in between the relief structures without the need for additional liftoff or annealing steps. Micelle size, dip coating speed, and height of the relief pattern were identified as important parameters to achieve a successful selective deposition. Finally, a single layer of patterned gold nanoparticles was formed inside the micropattern using an oxygen plasma treatment.

7. Gadolinium -niobates and -tantalates: Amorphous High-k Materials by Aqueous CSD - Dewulf, D.; Hardy, A.; Van Elshocht, S.; De Dobbelaere, C.; Wang, W. C.; Badylevich, M.; Afanas'ev, V. V.; De Gendt, S.; Van Bael, M.K.
In this work, compositional series of Gd-Nb-oxides and Gd-Ta-oxides are investigated as new potential high-k materials. Ultrathin oxide films in the range of 5-25 nm are deposited by spincoating. XRD and AFM show that the films are amorphous and smooth (RMS < 1 nm). Dielectric constants are derived from capacitance voltage (CV) measurements and EOT extraction. K values of the Gd-Nb-Ox series range from 13-16 while higher k values are obtained for the Gd-Ta-Ox series ranging from 15-19. For the Gd-Nb-Ox series, a higher k value is obtained for the most Gd-rich composition, while the opposite trend for the Gd-Ta-Ox...

8. Systematic evaluation of thermal and mechanical stability of different commercial and synthetic photocatalysts in relation to their photocatalytic activity - Ribbens, S.; Beyers, E.; SCHELLENS, Kevin; MERTENS, Mieke; Ke, X.; Bals, S.; Van Tendeloo, G.; Meynen, V.; Cool, P.
The effect of thermal treatment and mechanical stress on the structural and photocatalytic properties of eight different (synthetic and commercial) photocatalysts has been thoroughly investigated. Different mesoporous Ti-based materials were prepared via surfactant based synthesis routes (e.g. Pluronic 123, CTMABr = Cetyltrimethylammonium bromide) or via template-free synthesis routes (e.g. trititanate nanotubes). Also, the stabilizing effect of the NaOH/NH4OH post-treatment on the templated mesoporous materials and their photocatalytic activity was investigated. Furthermore, the thermal and mechanical properties of commercially available titanium dioxides such as P25 Evonik (R) and Millenium PC500 (R) were studied. The various photocatalysts were analyzed with N-2-sorption, X-ray...

9. Analytical TEM study of CVD diamond growth on TiO2 sol-gel layers - Lu, Ying-Gang; Verbeeck, Johan; Turner, Stuart; Hardy, An; Janssens, Stoffel D.; De Dobbelaere, Christopher; Wagner, Patrick; Van Bael, Marlies K.; Haenen, Ken; Van Tendeloo, Gustaaf
The early growth stages of chemical vapor deposition(CVD) diamond on a sol-gel TiO2 with buried ultra dispersed diamond seeds(UDD)have been studied. In order to investigate the diamond growth mechanism and understand the role of the TiO2 layer in the growth process, high resolution transmission electron microscopy(HRTEM), energy-filtered TEM and electron energy loss spectroscopy(EELS)techniques were applied to cross sectionaldiamond film samples. We find evidence for the formation of TiC crystallites inside the TiO2 layer at different diamond growth stages. However, there is no evidence that diamond nucleation starts from these crystallites. Carbon diffusion into the TiO2 layer and the chemical bonding...

10. Generalized approach to the description of recombination kinetics in bulk heterojunction solar cells???extending from fully organic to hybrid solar cells - Conings, Bert; Baeten, Linny; Boyen, Hans-Gerd; Spoltore, Donato; D'Haen, Jan; Van Bael, Marlies K.; Manca, Jean V.
Lately, research efforts in photovoltaics towards hybrid solar cells based on nanostructured metal oxides and conjugated polymers have been intensifying. However, very limited effort has been spent so far to investigate their recombination kinetics in comparison with their fully organic counterpart. In this work, impedance spectroscopy under different illumination intensities is used to probe the recombination kinetics of hybrid solar cells based on ZnO nanorod arrays and poly(3-hexylthiophene). A recombination-based model developed for fully organic solar cells is effectively applied in our hybrid solar cells, demonstrating their similarity in device physics and establishing the nanorod array/polymer compound as true bulk...

11. Properties and thermal stability of solution processed ultrathin, high-k bismuth titanate (Bi2Ti2O7) films - HARDY, An; Van Elshocht, S.; DE DOBBELAERE, Christopher; Hadermann, J.; Pourtois, G.; De Gendt, S.; Afanas'ev, V. V.; Van Bael, M. K.
Ultrathin bismuth titanate films (Bi2Ti2O7, 5-25 nm) are deposited onto SiO2/Si substrates by aqueous chemical solution deposition and their evolution during annealing is studied. The films crystallize into a preferentially oriented, pure pyrochlore phase between 500 and 700 degrees C, depending on the film thickness and the total thermal budget. Crystallization causes a strong increase of surface roughness compared to amorphous films. An increase of the interfacial layer thickness is observed after anneal at 600 degrees C, together with intermixing of bismuth with the substrate as shown by TEM-EDX. The band gap was determined to be similar to 3 eV...

12. Properties and thermal stability of solution processed ultrathin, high-k bismuth titanate (Bi2Ti2O7) films - HARDY, An; Van Elshocht, S.; DE DOBBELAERE, Christopher; Hadermann, J.; Pourtois, G.; De Gendt, S.; Afanas'ev, V. V.; Van Bael, M. K.
Ultrathin bismuth titanate films (Bi2Ti2O7, 5-25 nm) are deposited onto SiO2/Si substrates by aqueous chemical solution deposition and their evolution during annealing is studied. The films crystallize into a preferentially oriented, pure pyrochlore phase between 500 and 700 degrees C, depending on the film thickness and the total thermal budget. Crystallization causes a strong increase of surface roughness compared to amorphous films. An increase of the interfacial layer thickness is observed after anneal at 600 degrees C, together with intermixing of bismuth with the substrate as shown by TEM-EDX. The band gap was determined to be similar to 3 eV...

13. SnO2 thin films from an aqueous citrato peroxo Sn(IV) precursor - Stanulis, Andrius; Hardy, An; De Dobbelaere, Christopher; D'Haen, Jan; Van Bael, Marlies; Kareiva, Aivaras
In this work, tin(II) oxalate was studied as a novel chloride-free starting material for the preparation of a stable Sn-containing precursor solution. This precursor was applied for the chemical solution deposition (CSD) of transparent conducting coatings of SnO2 on Si/SiO2 substrates. An influence of synthesis parameters, such as pH, complexing agent to metal ion ratio on the stability of the citrato peroxo Sn(IV) precursor has been investigated in this study. Insights into the precursor chemistry and its thermal decomposition based on TG-DSC analysis are also presented. The obtained SnO2 films were characterized by high temperature X-ray diffraction (HT-XRD) and scanning...

14. SnO2 thin films from an aqueous citrato peroxo Sn(IV) precursor - STANULIS, Andrius; HARDY, An; DE DOBBELAERE, Christopher; D'HAEN, Jan; VAN BAEL, Marlies; Kareiva, Aivaras
In this work, tin(II) oxalate was studied as a novel chloride-free starting material for the preparation of a stable Sn-containing precursor solution. This precursor was applied for the chemical solution deposition (CSD) of transparent conducting coatings of SnO2 on Si/SiO2 substrates. An influence of synthesis parameters, such as pH, complexing agent to metal ion ratio on the stability of the citrato peroxo Sn(IV) precursor has been investigated in this study. Insights into the precursor chemistry and its thermal decomposition based on TG-DSC analysis are also presented. The obtained SnO2 films were characterized by high temperature X-ray diffraction (HT-XRD) and scanning...

15. SnO2 thin films from an aqueous citrato peroxo Sn(IV) precursor - STANULIS, Andrius; HARDY, An; DE DOBBELAERE, Christopher; D'HAEN, Jan; VAN BAEL, Marlies; Kareiva, Aivaras
In this work, tin(II) oxalate was studied as a novel chloride-free starting material for the preparation of a stable Sn-containing precursor solution. This precursor was applied for the chemical solution deposition (CSD) of transparent conducting coatings of SnO2 on Si/SiO2 substrates. An influence of synthesis parameters, such as pH, complexing agent to metal ion ratio on the stability of the citrato peroxo Sn(IV) precursor has been investigated in this study. Insights into the precursor chemistry and its thermal decomposition based on TG-DSC analysis are also presented. The obtained SnO2 films were characterized by high temperature X-ray diffraction (HT-XRD) and scanning...

16. Integrated bioprocess for long-term continuous cultivation of Clostridium acetobutylicum coupled to pervaporation with PDMS composite membranes - Van Hecke, Wouter; Vandezande, Pieter; Claes, Stan; Vangeel, Silvia; Beckers, Herman; Diels, Ludo; De Wever, Heleen
A continuous cultivation of Clostridium acetobutylicum ATCC 824 is described using a two-stage design to mimic the two phases of batch culture growth of the organism. A hydrophobic pervaporation unit was coupled to the second fermentor containing the highest solvent titers. This in situ product recovery technology efficiently decreased butanol toxicity in the fermentor while the permeate was enriched to 57??? 195 g L 1 total solvents depending on the solvent concentrations in the fermentor. By the alleviation of product inhibition, the glucose concentration could be increased from 60 to 126 g L 1 while the productivity increased concomitantly from 0.13 to 0.30 g L 1...

17. Crosslinked poly[1-(trimethylsilyl)-1-propyne] membranes: Characterization and pervaporation of aqueous tetrahydrofuran mixtures - Claes, Stan; Vandezande, Pieter; Mullens, Steven; Adriaensens, Peter; Peeters, Roos; Maurer, Frans H. J.; Van Bael, Marlies K.
To enhance their applicability in a broader range of pervaporation feed streams, poly[1-(trimethylsilyl)-1-propyne] (PTMSP) membranes have been successfully crosslinked, using a 3,3′-diazido-diphenylsulfone crosslinker. Both photochemical and thermal processes were used to activate the bis(azide) and thus initiate the crosslink reaction. The presented photochemical crosslink process, has an insufficient efficiency, due to the unreacted bis(azide) and the formation of by-products such as carboxylic acids. On the other hand, thermal annealing at temperatures of at least 160 °C allows successful crosslinking of PTMSP. In contrast to photochemical crosslinking, the bis(azide) completely decomposes after thermal treatment, rendering the membranes insoluble in solvents that...

18. Preparation and benchmarking of thin film supported PTMSP-silica pervaporation membranes - Claes, Stan; Vandezande, Pieter; Mullens, Steven; De Sitter, Kristien; Peeters, Roos; Van Bael, Marlies K.
Supported silica filled poly[1-(trimethylsilyl)-1-propyne] (PTMSP) membranes were optimised in terms of silica filler loading and top layer thickness, and applied in the pervaporative separation of dilute aqueous ethanol and butanol mixtures (5 wt.%). Addition of hydrophobic silica clearly increased the permeate flux at the expense of the alcohol/water selectivity. Based on its maximal pervaporation separation index (PSI) an optimum was found for a 25 wt.% silica filled membrane with a PTMSP separating layer of 2.4 μm thickness. This membrane exhibited a flux of 9.5 kg m−2 h−1 in combination with an ethanol/water separation factor of 18.3. In the pervaporation of...

19. Towards high???performance biopackaging: barrier and mechanical properties of dual???action polycaprolactone/ZnO nanocomposites - Elen, K.; Murariu, M.; Peeters, R.; Dubois, Ph.; Mullens, J.; Hardy, A.; Van Bael, M.K.
The properties of nanocomposites of biodegradable polycaprolactone containing zinc oxide (ZnO) nanoparticles with diverse morphologies, that is, ZnO nanospheres, nanorods, and nanodisks are investigated. It is demonstrated for the first time that the dual action of the ZnO nanoparticles reduces the gas permeability of the nanocomposites via two mechanisms: first by the creation of a tortuous path and second by gas adsorption. Depending on the morphology of the particles, the oxygen permeability can be reduced by more than 60%. Tensile tests show that the nanocomposites remain very ductile. The nominal strain for all nanocomposites is higher than 500% before fracture...

20. Deposition of functionalized gold nanoparticles onto modified silicon substrates - Riskin, Alexander; De Dobbelaere, Christopher; Elen, Ken; D'Haen, Jan; Van Den Rul, Heidi; Mullens, Jules; Hardy, An; Van Bael, Marlies
In this report, an existing phase transfer method for the synthesis of alkylamine- or alkanethiol-functionalized gold nanoparticles (NPs) is investigated. A parameter study shows that the concentration of the gold salt used is important for the stability of the resulting sol, but has little effect on the final average particle size or the size distribution. By adding dodecanethiol before the reduction, the formation of NPs was inhibited, providing evidence for the autocatalytic pathway for the formation of metallic NPs in wet chemical synthesis proposed in the literature. The resulting functionalized gold NPs are deposited onto Si–OH, octadecyltrichlorosilane (OTS) or 3- mercaptopropyltrimethoxysilane modified SiO2/Si substrates. scanning electron microscope (SEM) is used to analyze...

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